Phil Bardsley had forced a fine save from Irish goalkeeper Shay Given before the home side's 23rd-minute winner.

Keane was allowed to advance from his own half to the edge of the box before his low drive slipped under the body of Scotland goalkeeper Allan McGregor.

Kenny Miller was denied a penalty and then forced a fine instinctive save from Given as Scotland pressed late on.

But it was the Irish who claimed the victory to end with a 100% record in the new tournament after earlier defeats of Northern Ireland and Wales.

Both sides made four changes following midweek victories that left them joint top of the table with six points each.

Winger James Forrest was handed his Scotland debut, while fellow 19-year-old Grant Hanley started for the first time, with fit-again Bardsley joining the Blackburn man in defence and Barry Robson in midfield.

Scotland were missing the experienced Gary Caldwell and the in-form James Morrison through injury, while Ross McCormack and Stephen Crainey dropped out.

Damien Delaney, Kevin Foley, Seamus Coleman and Keith Treacy were the unlucky men to drop out despite the 5-0 thrashing of Northern Ireland.

The strengthened Republic side settled first and, when Simon Cox evaded a couple of challenges in the box following a corner, Charlie Adam was in the way to block the dangerous, low cross-come-shot.

Scotland responded on the break and Adam sent a drive whizzing just over the crossbar from 20 yards.

Bardsley went one better with a blistering effort from all of 30 yards that veteran goalkeeper Shay Given turned on to the bar and over for a corner.

However, it was the Irish who took the lead, thanks in part to Scottish slackness.

Paul McShane shrugged off the challenges of Steven Naismith and Forrest before releasing Keane, who advanced from just inside his own half to the edge of the penalty box before releasing a powerful low drive.

It looked close enough to McGregor for the goalkeeper to block, but it somehow squeezed under the Rangers man's body for captain Keane's 49th goal for his country.

Miller was inches away from connecting with a Robson cross that flashed across the Irish goalmouth, while Adam and Naismith tested Given with shots straight at the goalkeeper.

However, the first-half ended with the Irish in front and seemingly happy to defend their lead.

Scotland were caught out shortly after the break by a clever Stephen Hunt free-kick that found Cox rolling clear of marker Robson, but the West Brom striker's low drive powered across the six-yard box and wide.

The Irish were looking increasingly comfortable and Keith Andrews flashed a 22-yard free-kick a foot over the crossbar.

Scotland lost playmaker Adam, who had been an injury doubt before the game, but the arrival of Barry Bannan as his replacement after 62 minutes breathed new life into the visitors.

Forrest missed a great opportunity for a scoring debut when Robson's deep cross found the Celtic winger on the edge of the six-yard box and the teenager volleyed wide.

Miller was booked for his protestations as the Scotland captain was manhandled by Hunt inside the six-yard box and claimed for a penalty.

Naismith squandered another chance when he swiped wide a Chris Maguire cross from eight yards then Given produced a fine point-blank save from a Miller overhead kick.

Scotland were now well on top, but Miller curled a shot centimetres wide after breaking clear and holding off his marker as the Republic survived to claim a hard-fought victory.